I can't find any reference to David keeping Goliath's sword after he used it to chop off the Philistine's head, but I like to think he did.
On a final note, I need to refrain from using the term "mutant." I never intended the living residents of Gath to be radiated mutants, but I accidentally used the term and it got stuck in my head. Oops.
On a final, final note, using a melee weapon instead of a gun in Gath yields 2x the xps for a kill. It's what Denzel Washington would want.